Don't do this to yourself, Admirals don't even have CoA on Zoro's level. You need to know when to stop so people don't shit on your favorite characters.
On topic, whoever Zoro fights will be stronger than BM and a much better fighter and that includes Shiryu too, BM is the weakest top tier and Zoro is already beyond fighting non top tiers after he pulverized a Yonkou RHM in less than 10 minutes, just 2 hits with AdCoC, there's literally no one in-between a RHM/FM and Admirals/Yonkou/Top tiers, he can only fight top tiers and whoever it may be is definitely stronger than one former Yonkou.
You can say that Zoro's opponent or even Luffy's next opponent will be Yonko level but you cannot say that they will for sure be stronger than Kaido. There are only a few people who could potentially be stronger than Kaido and that is due to power creeping by the author as the story progresses in a manga. The candidates are Dragon, Imu & Gorosei , Akainu, BB, Shanks and Mihawk.
Obviously we don’t know what the next arc is yet, but I’d be surprised if there was any big fights in it except maybe for Luffy. (Weevil?)
Zoro probably will only have one fight with an opponent of that calibre and that will be at EoS.
Btw, Cross Guild does have potential for bringing in Mihawk as Zoro’s EoS fight, which I’ve not seen until now. Quite easy to see Buggy and co as a chaotic third party, maybe even one that claims Pluton (and that’s why Croc is there).